Automatic yarn tension control



July 25, 1950 v. T. STACK 2,516,535

AUTOMATIC YARN TENSION CONTROL MECHANISM FOR KNITTING MACHINES Filed May 4, 1949 3 Sheets-Sheet l INVENTOR: Remix T/wmas ,SZack A TTORNE YS.

WI TNijES y 1950 v. T. STACK AUTOMATIC YARN TENSION CONTROL MECHANISM FOR KNITTING MACHINES 3 Sheets-Sheeb 2 Filed May 4, 1949 INVENTOR:

Iferzwn T/zomasfifaak, BY W w ATTORNEYS.

July 25, 1950 v. T. STACK 2,516,535

AUTOMATIC YARN TENSION CONTROL MECHANISM FOR KNITTING MACHINES Filed May 4, 1949 s Sheets-Sheet s INVENTOR: Vernon 7720171068 flinch,

. mam gm llllllllllllllllllllllfilll A Patented July 25, 1950 UNITED STATES PATENT OFFICE AUTOMATIC YARN TENSION CONTROL MECHANISM FOR KNITTING MACHINES Vernon Thomas Stack, Walkertown, N. 0. Application May 4, 1949, Serial No. 91,338

Claims. 1

This invention relates to yarn tension control mechanism for knitting machines, particularly circular knitting machines of the kind commonly employed in the commercial production of seamless hosiery and the like.

Full length or ladies stockings successively knitted upon circular machines as ordinarily constructed, differ considerably in length, this irregularity being due to the lack of proper control of the yarn as it is fed to the needles and consequent formation, in individual courses, of loops which differ in size and contour and which often create an undesirable streaked appearance in the stockings.

The chief aim of my invention is to overcome the above drawbacks, that is to say: to make possible the more accurate control of yarn feeding in such knitting machines with a view toward determining formation of the fabric loops which are uniform throughout individual courses, and thereby insure production of successive stockings which will all be of the same length and linkages, to actuate a yarn tensioning means.

The flow of electric current to the motor is governed by a reversing detector switch operated through a rider element from the sinkers or web holders of the knitting machine in such a way as to bring about compensative slackening of the yarn in the event that the fabric loops on the needles tend to tighten and force the sinkers outward, and compensative increase in the yarn tension as the sinkers recede inwardly when the fabric loops tend to become larger during the formation of individual fabric courses.

Other objects and advantages will appear from the following detailed description of the attached drawings, wherein Fig. 1 is a broken out view in elevation, of sufilcient of a standard circular stocking knitting machine conveniently embody- Fig. 3 is a fragmentary view of the machine, partly in elevation. and partly in vertical section, on a still larger scale taken as indicated by the angled arrows III III in Fig. 2.

Fig. 4 is a detail view in cross section taken as indicated by the angled arrows 1V-IV in Fig. 3.

Fig. 5 shows the electric motor, and the parts immediately associated therewith, in top plan.

Fig. 6 is a'sectional view taken as indicated by the angled arrows VI--VI in Fig. 5.

Figs. 7 and 8 are perspective views showing the component "parts of two limit switches incorporated in the tension control mechanism.

The needle cylinder IU of the circular knitting machine herein illustrated in Fig. 1 for convenience of exemplifying my invention, is mounted as usual on a bed H supported by machine frame I2, and surrounded adjacent its top by a sinker ring it. Through suitable mechanism (not shown), the needle cylinder If] is rotated and oscillated at different times during the knitting as required in the production of seamless hosiery. The yarn feed finger indicated at I5 is swingable into and outof active position about a pin IS in an upward projection ll of the latch guard ring l8 of the machine; and the knitting yarn Y is supplied from a cone C and, enroute to said feed 'finger, passes through guide eyes 29 and 2! respectively on an arm 22 extending laterally from the yarn tree post 23, and on the latch guard ring l8. In the interval between the guides 20' and 2|, the yarn Y passes over the restraining rolls 24 of a tensioning device 25, said rolls being revolvably supported in'longitudinally spaced upstanding lugs of a bracket 26 which is secured to the post 23, with capacity forangular adjustment, by a clamp screw 21. Fulcrumed on studs 23 at opposite ends of the bracket 26, is a rocker '28 having three arms with eyes 3'0 at their swinginwardly toward the needles by an encircling spring band 33 so as to yieldingly engage the sinker Wale loops-of the fabric.

The sinker actuating cams (not illustrated) are carried by a cap 3a which overlies the sinker ring [3, and

which is held against'rotation during round and round knitting'but allowed a limited independent rotary play during reciprocatory knitting likewise in the well known way.

The automatic yarn tension control mechanism, with which the present invention is more especially concerned, includes a direct current electric motor which is indicated at 35. As shown, the motor 35 is enclosed in a housing 36 afiixed to the post 23 behind the tensioning means 25 as best seen in Fig. 1. Through a spur pinion 3i and an intermeshing spur wheel 38 (Figs. and 6), the motor 35 is arranged to drive a shaft 39 supported for rotation in a bearing 40 within the channel hollow of a U-shaped bracket 4! secured shaft to the housing 36. A worm 42 on the shaft 39 is in turn arranged to drive a worm wheel 43 on a transverse shait 45 whereof the ends are journalled in the opposite side portions 46 and 41 of the channel bracket 4|. Keyed to the shaft 45 is an arm 48 which, by means of alink 49, is connected toan arm 50 (Fig. 1) on :the rocker 29 of the tensioning means 25. The

swing of arm 48 is restricted to a prescribed range rbyclimit switches 5| and'56 supported within the channel hollow of the bracket 4|, and

arranged to be automatically opened to interrupt current flow to the motor 35 when said arm is moved "up and down beyond said range as will be more fully explained later. The fixed contact -:of switch .251 is in the form of an angular lug 52 which :is secured, with interposition of insulation,-.1Jothe .outer flange :46 of bracket M at 53. Themovable contact of switch 5! is in the form cfiafinger =54 rfulcrumed at 55 with interposition of insulation, and having apendent projection Eda in .the path of arm 48. The fixed contact of limit-switch 55 is likewise in the form of a lug 51 secured, with interposition of insulation, to the bottom web of the bracket 4! at '58, and the movable contact'of said switch is in the form of'a finger .59 ifulcrumed, likewisewith interpositionoi insulation, at 50011 the upstanding ear 51a of the aforesaid lug 51. As shown, the tail 58a of contact finger 59 extends into the path of a radial projection 6| on shaft 45.

Supply of :electric :current to the motor 35 'to drive it in one direction or the other is governed by a reversing detector switch comprehensively designated-65 in Figs. 1-4. This detector switch 55 has a contact arm 56 which is subject to an adjustable spring 61, and which is pivoted on an upstanding stud-68 inan elongate box-like casing '69 of non-conductive material such as hard rubber, so as to be sw ingable between a, pair of fixed contacts in and H at opposite sides of said casing. By means of the regulating screw-at 12, the casing 69 can be bodily adjusted about the stud '58 as an axis for a purpose also later explained, the end of said screw bearing against the bracket 89 as shown in Fig. 2. The detector switch 65 is ailixed to a slide l3 so as to be constrained to endwise movement in a bracket M disposed radially of a needle cylinder Ill and secured toanother fixed. post 15 on the machine. A springpressedjstud 15 (Fig. 3) acting upon a downward projection l3a at'the outer end of slide 13, tends to retract the detector switch 55 from its active position which is determined by engagement of an adjustable stop screw 11 in said downward projection, with theouter edge of the bracket '15.

The detector switch 55 is normally maintained in active position by means including a bell crank lever '18 which is pivoted. at E on a bearing bracket 85 reaching laterally from the post 15. The pendant'arm 18a of the-bell crank lever 18 presses against the downward projection [30. .ofislide 13,

while the horizontal arm 18b of said lever is connected, by a Bowden wire 8|, to a finger 82 (Fig. 1) pivoted to a bracket 83 on the base plate 84 of the machine. As shown, the finger 82 bears against the edge of cam disk 32 which, for the purposes of my invention, is provided with two circumferentially spaced depressions 85 and 86. Normally, with the detector switch 65 in active position as in Figs. 2 and 3, the short extremity 66a of its movable contact 66 bears against the protruding outer convex edge of a segmental rider element which is lodged in a, slot 9| in the side of a sinker cap ring 34, with its concave inner edge bearing against the butt ends of a plurality of the sinkers S. The rider element 89 is pivoted about a stud 92 on the sinker cap ring i3, and its swing is limited by coaction of a notch 98a in its outer end with a stop stud 93.

Direct current .for operation of the motor 35 may be obtained, as diagrammatically shown in Fig.2,fr0m an alternating current source by use of a transformer 95 having a split secondary whereof the two coil sections are designated 96 and 91. The current induced in the coils 95 and 91' at suitably reduced voltage is converted to direct current by rectifiers conventionally indicatedat 98 and 9S. Extendingfrom the rectifier 93 to one brush of the motor 35, is a conductor .582 in which a master switch [03 is interposed, the other motor brush being connected by another conductor H35 to the movable contact 65 of detector switch 55. Leading from the rectifier 99 to the fixed contact'52 of limit switch 5| is a conductor I06. The movable contact 54 of limit switch .55 is connected in circuit with the fixed contact is of detector switch 65 through still another conductor Jill. The other fixed contact H of thedetector switch 65 is in turn connected to the fixed contact 51 of limit switch 55 by a conductor 508, and the movable contact 59 of the latter switch to the terminal 109 of the secondary coil section 96 of transformer 95 by a conductor H0.

vBy reason of the described construction and arrangement of the constituent parts of improved automatic yarn tension control mechanism, it will be seen that, upon the slightest outward movement of the-sinkers S in the event of any tendency of the loops on the needles N to tighten, the rider element 99 will be correspondingly shifted and the movable contact {is of detector switch 65 swung from its normal neutral position into engagement with the fixed contact l0. As a consequence, current will flow to the motor 35 from the transformer coil 9? by way of the terminal HM, conductor Hi6, limit switch 5!, conductor till, the fixed and movable contacts M and 68 of detector switch 65, conductor m5 and conductor I62 to drive said motor in one direction, whereby, through the speed reduction gearing and linkages associated with said motor, the fingers 30 of the tensioning device will be momentarily raised to relieve the tension on the yarn Y. On the other hand, in the event that the loops on the needles should tend to slacken and allow the sinkers to recede toward the needles, the rider element 9%), in following up, will cause the movable contact 66 of detector switch 65 to be swung from its normal neutral position into engagement with fixed contact H of said switch. When this action takes place, current will flow in the opposite direction :from the transformer coil 95 to the motor 35 by way of conductor HI], limit switch 56, conductor I88, fixed and movable contacts 1' and 66 of detector switch 65 and conductor Hi5, whereby, through the gearing and linkages associated with said motor, the fingers 3!] of tension device 25 will be swung downward to momentarily increase the tension on the yarn. In this way, the tension of the yarn will be compensatively varied for maintenance of a uniform loop size during the knitting of successive courses of the fabric. If the yarn should break and the fingers 33} of the tensioning device 25 for this or any other reason swing in either direction beyond the range prescribed by the limit switches 51 and 55, the latter will be opened to interrupt current flow to the motor 35. Preparatory to the heel and toe knitting phases of the machine, the detector switch 65 is bodily retracted to inactive position by pressure of the spring-backed plunger 16 (Fig. 1) upon the slide #3 as the pull on the bell crank lever 78 is relieved when the finger 32 falls into the peripheral notches 85 and 8B of cam 32 on the pattern shaft 3! of the machine. The mechanism may be rendered inoperative when its use is not desired or required, by opening the master switch I03 as will be readily understood.

The position of the end 65a of the switch element 66 relative to the rider element may be accurately varied through adjustment of the housing 69 about the stud 68 by means of the screw '12 to predetermine the size limits of the smallest and largest loops made during a knitting cycle of the machine.

Having thus described my invention, I claim:

1. Automatic yarn tension control mechanism for a knitting machine having a plurality of independent needles, individually cooperative sinkers spring-urged toward the needles, and a means for tensioning a knitting yarn enroute to the needles, said control mechanism including a detector adapted to be influenced by the sinkers in the event of any tendency of the fabric loops formed by the needles to tighten or slacken, and interposed means for actuating the tensioning means to compensatively increase or decrease the tension on the yarn for maintenance of a uniform loop size in individual courses of the fabric produced by the machine.

2. Antomatic yarn tension control mechanism, according to claim 1, wherein the tensioning means comprises a pivoted element in engagement with the yarn in the interval between two yarn guides; and further including means for rendering the control mechanism inoperative upon movement of said pivoted element beyond prescribed limits in opposite directions.

3. Automatic yarn tension control mechanism for a knitting machine having a plurality of independent needles, individually cooperative sinkers spring-urged toward the needles, and means for tensioning a knitting yarn enroute to the needles, said control mechanism including a reversible motor for actuating the yarn tensioning means, a rider element bearing against and adapted to be influenced by movement of the sinkers in the event of any tendency of fabric loops on the needles to tighten or slacken, a detector arranged to be actuated by the rider element, and interposed means whereby the motor is operated in one direction or the other to correspondingly actuate the tensioning means and thereby compensatively vary the tension on the yarn for maintenance of a uniform 100p size in individual courses of the fabric produced by the machine,

4, Automatic yarn tension control mechanism, according to claim 3, wherein the tensioning means comprises a pivoted element for depressing the yarn in the interval between a pair of spaced guides; and further includin means for rendering the motor means inoperative upon movement of said pivoted element beyond prescribed limits in opposite directions.

5. Automatic yarn tension control mechanism, according to claim 3, for a circular knitting machine with sinkers slidable in radial grooves of a sinker ring surrounding a rotary needle cylinder, an encircling band for urging the sinkers toward the needles and a normally stationary cap ring superposed upon the sinker ring, and wherein the rider element is pivoted on the cap ring and bears against the butt ends of the sinkers.

6. Automatic yarn tension control mechanism for a knitting machine havin a plurality of independent needles, individually cooperative sinkers spring-urged toward the needles, and means for tensioning a knitting yarn enroute the needles, said control mechanism including a reversible electric motor for actuating the tensioning device, a rider element bearing against and adapted to be influenced by movement of the sinkers in the event of any tendency of the loops formed by the needles to tighten or slacken, a reversing detector switch arranged to be actuated by the rider element and operative to determine the flow of electric current to the reversible motor in one direction or the other to correspondingly actuate the tensioning means and thereby effect compensatively increase or decrease the tension on the yarn for maintenance of a uniform loop size in individual courses of the fabric produced by the machine.

7. Automatic yarn tension control mechanism for a knitting machine, according to claim 6, wherein the tensioning means comprises a pivoted element for depressing the yarn in the interval between a pair of spaced guides, and further including a pair of limit switches in circuit with the motor adapted to be opened to stop the motor upon movement of said pivoted element beyond prescribed limits in opposite directions.

8. Automatic yarn tension control mechanism according to claim 6, for a knitting machine wherein the tensioning means comprises a pivoted element for depressing the yarn between a pair of spaced guides; and further including a shaft driven through speed reduction gearing from the electric motor, an arm on said shaft coupled to the pivoted element of the yarn tensioning device, and a pair of limit switches in circuit with the motor arranged to be opened by said arm upon movement thereof beyond prescribed limits in opposite directions.

9. Automatic yarn tension control mechanism according to claim 6, for a knitting machine wherein the tensioning means comprises a pivoted element for depressing the yarn between a pair of spaced guides; and further including a shaft driven through speed reduction gearing from the electric motor, and an arm on said shaft coupled to the pivoted element of the yarn tensioning device.

10. Automatic yarn tension control mechanism, according to claim 6, wherein the detector switch comprises a medially pivoted contact with one end thereof normally positioned centrally between a pair of fixed contacts in circuit with the motor, and with the other end thereof bearing against the rider element.

VERNON THOMAS STAQISi retainers aria 

